Carrier metal catalyst, manufacturing method thereof, and fuel cell

ABSTRACT

The carrier metal catalyst achieves suppression of internal resistance of a fuel cell. A carrier metal catalyst includes: a carrier powder; and metal fine particles supported on the carrier powder; wherein: the carrier powder is an aggregates of carrier fine particles; the carrier fine particles includes a chained portion structured by a plurality of crystallites being fusion bonded to form a chain; the carrier fine particles include titanium oxide; the carrier fine particles are doped with an element having a valence different from a valence of titanium; the titanium oxide of the carrier powder has an anatase phase/rutile phase ratio of 0.2 or lower; the metal fine particles have a mean particle size of 3 to 10 nm; the metal fine particles include platinum; and a cell resistance measured under standard conditions of a fuel cell prepared using the carrier metal catalyst is 0.090 Ω·cm 2  or lower.

FIELD OF THE INVENTION

The present invention relates to a carrier metal catalyst and amanufacturing method thereof. The carrier metal catalyst of the presentinvention is suitably used as an anode electrode catalyst of a fuelcell.

BACKGROUND OF THE INVENTION

Patent Literature 1 discloses usage of a carrier metal catalyst preparedby allowing a metal catalyst to be supported on a support structuredwith titanium oxide doped with a dissimilar metal.

PRIOR ART DOCUMENTS Patent Literature

-   [Patent Literature 1] WO 2016/203679

Non-Patent Literature

-   [Non-Patent Literature 1] Journal of catalysis 161, 560-569 (1996):    Charge Transfer in Metal Catalysts Supported on Doped TiO₂: A    Theoretical Approach Based on Metal-Semiconductor Contact Theory

SUMMARY OF INVENTION Technical Problem

However, the fuel cell of Patent Literature 1 cannot be regarded ashaving sufficiently low internal resistance, and thus reduction ofinternal resistance is desired.

The present invention has been made by taking these circumstances intoconsideration. An object of the present invention is to provide acarrier metal catalyst which can reduce internal resistance of the fuelcell.

Means to Solve the Problem

According to the present invention, a carrier metal catalyst,comprising: a carrier powder; and metal fine particles supported on thecarrier powder; wherein: the carrier powder is an aggregates of carrierfine particles; the carrier fine particles comprise a chained portionstructured by a plurality of crystallites being fusion bonded to form achain; the carrier fine particles include titanium oxide; the carrierfine particles are doped with an element having a valence different froma valence of titanium; the titanium oxide of the carrier powder has ananatase phase/rutile phase ratio of 0.2 or lower; the metal fineparticles have a mean particle size of 3 to 10 nm; the metal fineparticles include platinum; and a cell resistance measured understandard conditions of a fuel cell prepared using the carrier metalcatalyst is 0.090 Ω·cm² or lower; is provided.

When the tetravalent titanium (Ti⁴⁺) in the titanium oxide (TiO₂) isreduced to Ti³⁺, conductivity is obtained. On the surface of thesupport, Ti³⁺ is localized in a region at the vicinity of the metal fineparticles. The larger the area of the Ti³⁺ region, the conductivity ofthe carrier metal catalyst increases, thereby reducing the internalresistance of the fuel cell using such carrier metal catalyst.

The present inventors have conducted intensive research, and have foundthat when the heat treatment after allowing the metal colloidalparticles to be adsorped onto the support is carried out at atemperature of 920° C. or higher, the area of Ti³⁺ becomes larger,thereby increasing conductivity of the carrier metal catalyst. Inaddition, when the heat treatment is carried out at a temperatureexceeding 1100° C., the metal fine particles would aggregate on thesupport and becomes large, thereby increasing the distance between themetal fine particles. As a result, the conductivity of the carrier metalcatalyst is decreased.

From these knowledge, it became apparent that carrier metal catalyst inwhich the mean particle size of the metal fine particles is 3 to 10 nmand the cell resistance measured under standard conditions is 0.09 Ω·cm²or lower can be obtained when the heat treatment is carried out in atemperature range of 920 to 1100° C., thereby leading to completion ofthe invention.

Here, when the heat treatment after allowing the metal colloidalparticle to be adsorped onto the support is carried out at a temperatureof 900° C. as in Patent Literature 1, the area of Ti³⁺ region was notsufficiently large, and thus the cell resistance measured under standardconditions was 0.10 Ω·cm² or higher.

BRIEF DESCRIPTION OF THE DRAWINGS

The above further objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a model diagram of a catalyst structure of carrier metalcatalyst 100.

FIG. 2 shows a view in which carrier fine particles 150 are taken fromFIG. 1.

FIG. 3 shows a condition of branch 160 of the carrier fine particles 150of FIG. 1.

FIG. 4 shows a gas diffusion route of FIG. 1.

FIG. 5 shows one example of a distribution of gaps 110 contained in thecarrier powder.

FIG. 6A is a TEM image of carrier metal catalyst 100 of Example 1.

FIG. 6B is a TEM image of carrier metal catalyst 100 of Example 2.

FIG. 7 is a model diagram of a fuel cell.

FIG. 8 is a sectional view which is cut through the center of burner 2of a manufacturing apparatus 1 for manufacturing the carrier powder.

FIG. 9 is an enlarged view of region X in FIG. 8.

FIG. 10 is a sectional view taken along the line A-A of FIG. 8.

FIG. 11 is an enlarged view of region Y in FIG. 10.

FIG. 12 is a flow of supporting step and reduction step of metal fineparticles 130.

FIG. 13A is a XRD pattern of PtCo/Ta—TiO₂ and Pt/Ta—TiO₂.

FIG. 13B is an enlarged view of the vicinity of 35 to 55° in FIG. 13A.

FIG. 14 shows a result of measurement of I-V characteristics and cellresistance.

FIG. 15 shows an apparatus configuration of H₂ pump test.

FIG. 16 shows a polarization curve of an anode.

FIG. 17 shows a cyclic voltammogram of PtCo/Ta—TiO₂ catalyst andPt/Ta—TiO₂ catalyst.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained withreference to the drawings. Various distinctive features shown in thefollowing embodiments can be combined with each other. In addition, aninvention can be established independently for each of the distinctivefeatures.

1. Carrier Metal Catalyst 100

As shown in FIGS. 1 to 4, the carrier metal catalyst 100 comprises acarrier powder which is an aggregate of carrier fine particles having achained portion structured by fusion bonding a plurality of crystallites120 into a chain, and metal fine particles 130 being supported on thecarrier powder.

A cell resistance measured under standard conditions of a fuel cellprepared using the carrier metal catalyst 100 is 0.090 Ω·cm² or lower,preferably 0.085 Ω·cm² or lower, more preferably 0.080 Ω·cm² or lower,further preferably 0.075 Ω·cm² or lower, and even preferably 0.070 Ω·cm²or lower. The lower limit of the cell resistance is not particularlylimited, and is, for example, 0.010 Ω·cm². Standard conditions will beexplained in detail in the Examples.

Hereinafter, each of the constituents will be explained.

1-1. Carrier Fine Particles 150 and Carrier Powder

As shown in FIG. 1, in the carrier fine particles 150, athree-dimensional gap 110 surrounded by the branch 160 and poresexisting between a plurality of branches is formed. Here, a plurality ofcrystallites 120 structuring the carrier fine particles 150 is fusionbonded to form a chained portion, thereby forming the branch 160. Gasdiffusion route to diffuse and transfer oxygen as the oxidant and/orhydrogen as the fuel to the carrier metal catalyst 100 is formed by thethree-dimensional arrangement of the carrier fine particles 150described above.

As shown in FIGS. 1 to 3 as an example of structure model of the carriermetal catalyst, the carrier fine particles 150 comprise four pores of afirst pore surrounded by points b1, b2, b5, b4, and b1, where thebranches link with each other (may be referred to as branching points,or merely as branch); a second pore surrounded by branching points b1,b2, b3, and b1; a third pore surrounded by branching points b2, b3, b6,b7, b5, and b2; and a fourth pore surrounded by branching points b1, b3,b6, b7, b5, b4, and b1. Here, when a plane surrounded by the branchingpoints of each of the pores (first to fourth pores) is taken as the poreplane, the gap 110 is a three-dimensional space surrounded by the fourpore planes. The carrier fine particles 150 comprise a plurality ofpores surrounded by a plurality of branching points in which a pluralityof branches link with each other. Further, the three-dimensional spaces(gaps) which are surrounded by the plurality of pores are providedsequentially, thereby structuring the carrier fine particles.Accordingly, the gap serves as the gas diffusion route (gas diffusionpath) of oxygen, hydrogen and the like. FIG. 4 shows the gas diffusionroute in FIG. 1. In FIG. 4, one example of the gas diffusion route (gasdiffusion path) of gap 110 is shown. Flow (gas diffusion route) 170 ofoxidant (gas), fuel gas and the like can flow in the desired directionvia the gap 110 as shown in FIG. 4. That is, the gap 110 serves as thegas diffusion route.

Here, as a simple structure of the carrier fine particles 150, thecarrier fine particles can have only one pore (for example, the firstpore surrounded by the branching points b1, b2, b5, b4, and b1). In suchcase, a gap 110 having a thickness of the crystallite grain of thecrystallite 120 is provided. As a more simple structure, the carrierfine particles 150 can have one or more branches. In such case, thebranches within the carrier fine particles 150 prohibits cohesion of thecrystallites, thereby providing gap 110 between the crystallites.

Here, the “pore” mentioned above can also be mentioned as closed curve(closed loop). Otherwise, it can be said that a gap 110 surrounded by aclosed plane including the afore-mentioned plurality of branching points(for example, branching points b1 to b7) is provided. As the branchingpoints b1 to b7, the center of gravity of the crystallite of the metaloxide structuring the carrier fine particles 150 in which the branchesconnect with each other can be taken as the branching point, or anarbitrary point in the crystallite can be taken as the branching point.

The size of the crystallite 120 is preferably 1 to 30 nm, morepreferably 5 to 15 nm. The size is, particularly for example, 1, 5, 10,15, 20, 25, and 30 nm, and can be in the range between the two valuesexemplified herein. The size of the crystallite 120 (crystallitediameter) can be obtained in accordance with a Sheller formula usinghalf-width in the XRD pattern peak.

The aggregate of the carrier fine particles 150 is in the form of apowder. Such aggregate is referred to as “carrier powder”.

The mean particle size of the carrier fine particles 150 in the carrierpowder is in the range of 0.1 μm to 4 μm, preferably in the range of 0.5μm to 2 μm. The mean particle size of the carrier fine particles 150 canbe measured with a laser diffraction/scattering particle sizedistribution analyzer.

The specific surface area of the carrier powder is preferably 12 m²/g ormore, and is more preferably 25 m²/g or more. The specific surface areais, for example, 12 to 100 m²/g, particularly for example, 12, 15, 20,25, 30, 35, 40, 45, 50, 60, 70, 80, 90, or 100 m²/g, and can be in therange between the two values exemplified herein.

On example of the distribution of gap 110 contained in the carrierpowder is shown in FIG. 5. Distribution of gap 110 can be obtained bymeasuring the volume of the three-dimensional gap of the carrier powder,using a mercury porosimetry. In FIG. 5, volume per one gap is obtainedfrom the measured value of the volume and the number of the gaps, andthen a diameter of a sphere is obtained by converting the volumeobtained into a volume of a sphere (sphere equivalent diameter obtainedby mercury press-in method). FIG. 5 shows a cumulative size distributionof the diameter of the sphere. As shown in FIG. 5, the carrier powderpreferably has a gap of 11 nm or less (primary pore) and a gap of largerthan 11 nm (secondary pore). As such, gas diffusion route in thecatalyst layer of the fuel cell can be provided.

The carrier powder preferably has a porosity of 50% or more, and morepreferably a porosity of 60% or more. The porosity is, for example, 50to 80%, particularly for example, 50, 55, 60, 65, 70, 75, or 80%, andcan be in the range between the two values exemplified herein. Porositycan be obtained by mercury press-in method or by FIB-SEM.

The carrier powder preferably has a repose angle of 50 degrees or less,and more preferably a repose angle of 45 degrees or less. In such case,the carrier powder has a similar flowability as flour, and thus handlingis simple. The repose angle is, for example, 20 to 50 degrees,particularly for example, 20, 25, 30, 35, 40, 45, or 50, and can be inthe range between the two values exemplified herein. The repose anglecan be obtained by drop volume method.

The carrier fine particles 150 are doped with an element having avalence different from the valence of titanium. As the element having avalence different from the valence of titanium, at least one is selectedfrom rare earth element represented by yttrium, group 5 elementrepresented by niobium and tantalum, group 6 element represented bytungsten, and group 15 element represented by antimony. By doping withsuch element, the carrier fine particles can be provided withconductivity. Among such elements, group 5 element represented byniobium and tantalum, and group 6 element represented by tungsten arepreferable, and tantalum, niobium and tungsten are especiallypreferable. Tantalum and tungsten are especially preferable due to theirlarge solid solubility limit. Here, when non-doped, anatase phase oftitanium oxide can be converted into rutile phase by heat treatment atapproximately 500° C. On the other hand, replacement by solid solutionof the dopant can raise the phase conversion temperature to 1000° C. orhigher. Accordingly, when titanium oxide of carrier fine particles 150contains a dopant, manufacture of the carrier fine particles 150 andcarrier powder by the method described in “3. Method for ManufacturingCarrier Powder” would be especially meaningful.

Conductivity of the carrier powder is preferably 0.001 S/cm or higher,and is more preferably 0.01 S/cm or higher. The conductivity is, forexample, 0.01 to 1000 S/cm, particularly for example, 0.01, 0.1, 1, 10,100, or 1000 S/cm, and can be in the range between the two valuesexemplified herein. Conductivity can be measured in accordance with theJIS standard (JIS K 7194).

The carrier fine particles 150 have a branch 160 comprising a chainedportion which is structured by fusion bonding a plurality ofcrystallites 120 into a chain. The branch 160 itself has a nature toallow electrons to flow. As shown in FIGS. 1 to 4, the carrier fineparticles 150 have a plurality of branches 160, and the branches connectwith each other at branching points (b1 to b7), by which a network isstructured. Electrons flow among the branches, thereby providingelectrical conductivity. Accordingly, the branches 160 of the carrierfine particles 150 shown by the dotted line from point PO in FIG. 1itself structures an electron conduction route (electron conductionpath) 140.

In the present embodiment, the carrier fine particles 150 includetitanium oxide, and the ratio of the titanium oxide contained in themetal oxide in the carrier fine particles 150 is preferably 50 mol % ormore. This ratio is, particularly for example, 50, 60, 70, 80, 90, 95,or 100 mol %, and can be in the range between the two values exemplifiedherein.

The ratio of anatase phase/rutile phase of the titanium oxide in thecarrier powder is 0.2 or lower. In such case, the characteristics of therutile phase would appear strongly, resulting in higher thermodynamicstability and it becomes easier to provide conductivity when doped. Theratio is, particularly for example, 0, 0.05, 0.1, 0.15, or 0.2, and canbe in the range between the two values exemplified herein. The ratio canbe obtained by (peak intensity at 2θ=25.16 degrees)/(peak intensity at2θ=27.24 degrees) in the XRD pattern. This is since the peaks at2θ=25.16 degrees and 2θ=27.24 degrees are peaks derived from thepresence of the anatase phase and the rutile phase, respectively.

1-2. Metal Fine Particles 130

The metal fine particles 130 are fine particles of metal or alloy whichcan function as a catalyst. The metal fine particles 130 includeplatinum. The mean particle size of the plurality of metal fineparticles 130 supported on the carrier powder is preferably 3 to 10 nm,more preferably 3 to 10 nm. The mean particle size is, particularly forexample, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, or 20 nm, and can be in the range between the two values exemplifiedherein. When the mean particle size of the metal fine particles 130 issmaller than 3 nm, the metal fine particles would dissolve along withthe progress of the electrode reaction. On the other hand, when the meanparticle size of the metal fine particles 130 is larger than 10 nm, theelectrochemical active area would become small, and thus the desiredelectrode property cannot be achieved. The mean particle size of themetal fine particles 130 can be obtained by measuring the diameter ofthe circumscribed circle of all the metal fine particles 130 in the TEMimage of the carrier metal catalyst 100 (such as those shown in FIG. 6Aand FIG. 6B), and then calculating the arithmetic mean of the measureddiameter.

The metal fine particles 130 preferably comprise a core, and a skinlayer covering the core. The core preferably comprises an alloy of anoble metal and a transition metal. The skin layer preferably comprisesa noble metal. As the noble metal, platinum is preferable. As thetransition metal, cobalt (Co) or nickel (Ni) are preferable, and cobaltis especially suitable.

The metal fine particles 130 preferably contain titanium as a solidsolution, and the amount of titanium dissolved in the core is preferablylarger than the amount of titanium dissolved in the skin layer. As such,when titanium is dissolved more in the core, activity of the core can beimproved.

The amount of the metal fine particles being supported is preferably 1to 50 mass %, more preferably 5 to 25 mass %. The amount being supportedis, particularly for example, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or50 mass %, and can be in the range between the two values exemplifiedherein.

The electrochemical active area of the carrier metal catalyst 100 ispreferably 20 m²/g or more. This are is, for example, 20 to 200 m²/g,and is, particularly for example, 20, 30, 40, 50, 60, 70, 80, 90, 100,110, 120, 130, 140, 150, 160, 170, 180, 190, or 200 m²/g, and can be inthe range between the two values exemplified herein. The electrochemicalactive area can be obtained by cyclic voltammetry.

2. Fuel Cell 200

A model diagram of the fuel cell according to the present invention isshown in FIG. 7. In FIG. 7, the fuel cell 200 is structured by aligningthe catalyst layer 220A and the gas diffusion layer 210A on the anode201 side, and the catalyst layer 220K and the gas diffusion layer 210Kon the cathode 202 side, facing each other with the electrolyte membrane230 in between. That is, the gas diffusion layer 210A on the anode side,the catalyst layer 220A on the anode side, the electrolyte membrane 230,the catalyst layer 220K on the cathode side, and the gas diffusion layer210K on the cathode side are aligned in this order. By connecting theload 203 in between the anode 201 and the cathode 202 of the solidpolymer electrolyte fuel cell 200, power is output to the load 203.

At least one of the catalyst layer on the anode side 220A and thecatalyst layer on the cathode side 220K is preferably formed by thecarrier metal catalyst 100. More preferably, the catalyst layer on theanode side 220A is formed by the carrier metal catalyst 100. The carriermetal catalyst 100 has a larger resistance under oxygen atmosphere thanunder hydrogen atmosphere. Therefore, when the carrier metal catalyst100 is used for the catalyst layer on the anode side 220A, oxygenreduction reaction at the catalyst layer on the anode side 220A issuppressed when the fuel cell is started or terminated. Accordingly,even when the support of the catalyst layer on the cathode side 220K iscarbon, the corrosion reaction thereof is suppressed, therebysuppressing degradation of the power generation performance of the fuelcell.

As the catalyst other than the carrier metal catalyst 100, catalystsdisclosed in Patent Literature 1, catalysts prepared by allowing metalfine particles be supported on a support of ceramics other than titaniumoxide (for example, tin oxide), catalysts prepared by allowing metalfine particles be supported on carbon support can be mentioned forexample.

3. Method for Manufacturing Carrier Powder

First, referring to FIG. 8 to FIG. 11, the manufacturing apparatus 1which can be used for the manufacture of the carrier powder isexplained. The manufacturing apparatus 1 comprises a burner 2, a rawmaterial supplying unit 3, a reaction cylinder 4, a collector 5, and agas reservoir 6. The raw material supplying unit 3 comprises an outercylinder 13, and a raw material distribution cylinder 23.

The burner 2 is a cylinder, and the raw material supplying unit 3 isarranged in the burner 2. Burner gas 2 a is distributed between theburner 2 and the outer cylinder 13. The burner gas 2 a is used to form aflame 7 at the tip of the burner 2 by ignition. A high temperatureregion having a temperature of 1000° C. or higher is formed by the flame7. The burner gas 2 a preferably contains a combustible gas such aspropane, methane, acetylene, hydrogen, or nitrous oxide. In one example,a gas mixture of oxygen and propane can be used as the burner gas 2 a.The temperature of the high temperature region is 1000 to 2000° C. forexample, and is particularly for example, 1000, 1100, 1200, 1300, 1400,1500, 1600, 1700, 1800, 1900, or 2000° C., and can be in the rangebetween the two values exemplified herein.

A raw material solution 23 a for generating the carrier powder isdistributed in the raw material distribution cylinder 23. As the rawmaterial solution 23 a, the one containing a titanium compound is used.As the titanium compound, fatty acid titanium can be mentioned forexample. The number of carbon atoms in the fatty acid is, for example, 2to 20, preferably 4 to 15, and further preferably 6 to 12. As the fattyacid titanium, titanium octylate is preferable. The raw materialsolution 23 a can contain a metal compound for doping the carrier fineparticles 150. As the metal compound, fatty acid metal (Nb, Ta, W andthe like) salt can be mentioned for example. The number of carbon atomsin the fatty acid is, for example, 2 to 20, preferably 4 to 15, andfurther preferably 6 to 12. As the fatty acid metal salt, niobiumoctylate, tantalum octylate, and tungsten octylate are preferable. Themolar ratio of titanium compound:metal compound is arbitrarilydetermined to improve the conductivity of the carrier powder. Here, themolar ratio is preferably 0.8:0.2 to 0.99:0.01.

In the raw material solution 23 a, the titanium compound is preferablydissolved or dispersed in a non-aqueous solvent. As the non-aqueoussolvent, organic solvent represented by tarpen can be mentioned. Whenmoisture is contained in the raw material solution 23 a, the fatty acidtitanium can undergo hydrolysis and deteriorate. To prevent hydrolysisof the fatty acid titanium, the water content of the raw materialsolution 23 a is preferably 100 ppm or lower, and more preferably 50 ppmor lower. By preventing hydrolysis of fatty acid titanium, ratio of therutile phase in the titanium oxide can be improved.

Mist gas 13 a used for converting the raw material solution 23 a into amist is distributed in between the outer cylinder 13 and the rawmaterial distribution cylinder 23. When the mist gas 13 a and the rawmaterial solution 23 a are jetted together from the tip of the rawmaterial supplying unit 3, the raw material solution 23 a is convertedinto a mist. The mist 23 b of the raw material solution 23 a is sprayedinto the flame 7, and the titanium compound in the raw material solution23 a undergoes a thermal decomposition reaction in the flame 7.Accordingly, carrier powder which is an aggregate of carrier fineparticles 150 having a chained portion structured by fusion bonding thecrystallite 120 into a chain is generated. The mist gas 13 a is oxygenin one example.

The reaction cylinder 4 is provided between the collector 5 and the gasreservoir 6. The flame 7 is formed in the reaction cylinder 4. Thecollector 5 is provided with a filter 5 a and a gas discharging portion5 b. A negative pressure is applied to the gas discharging portion 5 b.Accordingly, a flow which flows towards the gas discharging portion 5 bis generated in the collector 5 and the reaction cylinder 4.

The gas reservoir 6 has a cylinder shape, and comprises a cold gasintroducing portion 6 a and a slit 6 b. A cold gas 6 g is introducedfrom the cold gas introducing portion 6 a into the gas reservoir 6. Thecold gas introducing portion 6 a is directed in a direction along thetangential line of the inner peripheral wall 6 c of the gas reservoir 6.Therefore, the cold gas 6 g introduced through the cold gas introducingportion 6 a into the gas reservoir 6 revolves along the inner peripheralwall 6 c. At the center of the gas reservoir 6, a burner insertion hole6 d is provided. The burner 2 is inserted through the burner insertionhole 6 d. The slit 6 b is provided in the vicinity of the burnerinsertion hole 6 d so as to surround the burner insertion hole 6 d.Accordingly, when the burner 2 is inserted through the burner insertionhole 6 d, the slit 6 b is provided so as to surround the burner 2. Thecold gas 6 g in the gas reservoir 6 is driven by the negative pressureapplied to the gas discharging portion 5 b, and is discharged from theslit 6 b towards the reaction cylinder 4. The cold gas 6 g can be anygas so long as it can cool the titanium oxide generated, and ispreferably an inert gas, for example, air. The flow speed of the coldgas 6 g is preferably two times or more of the flow speed of the burnergas 2 a. The upper limit of the flow speed of the cold gas 6 g is notparticularly limited, and is 1000 times the flow speed of the burner gas2 a for example. The ratio of flow speed of cold gas 6 g/flow speed ofburner gas 2 a is 2 to 1000 for example, and the ratio is particularlyfor example, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 100, 200, 500, or1000, and can be in the range between the two values exemplified herein.Here, in the present embodiment, a negative pressure is applied to thegas discharging portion 5 b to allow the cold gas 6 g to flow, however,a positive pressure can be applied to the gas introducing portion 6 a toallow the cold gas 6 g to flow.

In a case where the gas reservoir 6 is not provided, the outer airdirectly flows into the reaction cylinder from the gap between theburner and the reaction cylinder. Therefore, the outer air would turninto a turbulent flow in the reaction cylinder, thereby scattering mist,crystallite and carrier fine particles. Therefore, they cannot besufficiently heated by the flame, thereby resulting in generation oftitanium oxide having high ratio of anatase phase which is a metastablephase. On the other hand, in the present invention, the cold gas 6 g issupplied in the surroundings of the flame 7 through the slit 6 b, andthus the cold gas 6 g flow around the flame 7 as a laminar air flow.Therefore, the mist 23 b, crystallite 120, and the carrier fineparticles 150 would not be scattered by the cold gas 6 g, allowing themto move along the flame 7 and be heated sufficiently to progress thereaction. Accordingly, the ratio of the rutile phase of the titaniumoxide in the carrier fine particles 150 can be increased. In addition,after the carrier fine particles 150 come out of the flame 7, thecarrier fine particles 150 would be immediately cooled by the cold gas 6g, thereby allowing to maintain the structure having the chainedportion. The carrier fine particles 150 after cooling would be trappedby the filter 5 a and collected.

In the present invention, the carrier powder which is an aggregate ofthe carrier fine particles 150 can be manufactured by using themanufacturing apparatus 1. Here, a high-temperature region of 1000° C.or higher is formed at the tip of the burner 2 by the flame 7, and thetitanium compound is allowed to undergo a thermal decomposition reactionin this high-temperature region while supplying the cold gas 6 g throughthe slit 6 b to the surroundings of the high-temperature region. Thehigh-temperature region can be formed by plasma instead of the flame 7.

4. Method for Manufacturing Carrier Metal Catalyst 100

The method for manufacturing carrier metal catalyst 100 comprises asupporting step and a reduction step.

<Supporting Step>

In the supporting step, the metal fine particles 130 are supported onthe carrier powder. Such supporting can be performed by a reversemicelle method, a colloidal method, an impregnation method and the like.In the colloidal method, the supporting step comprises an adsorptionstep and a heat treatment step.

In the adsorption step, the metal colloidal particles are adsorped ontothe carrier powder. More particularly, the metal colloidal particlessynthesized by the colloidal method is dispersed in an aqueous solutionto prepare a dispersion, and then the metal colloidal particles areadded and mixed in the dispersion. Accordingly, the colloidal particlesare adsorped onto the surface of the carrier powder. The carrier powderhaving the colloidal particles adsorped thereon is then filtered anddried, thereby being separated from the dispersion medium. The metalcolloidal particles include platinum.

In the heat treatment step, the metal colloidal particles are subjectedto a heat treatment at 920 to 1100° C. after the adsorption step,thereby converting the metal colloidal particles into the metal fineparticles 130. The temperature of the heat treatment is, particularlyfor example, 920, 930, 940, 950, 960, 970, 980, 990, 1000, 1010, 1020,1030, 1040, 1050, 1060, 1070, 1080, 1090, or 1100° C., and can be in therange between the two values exemplified herein.

The heat treatment time is, for example, 0.1 to 20 hours, preferably 0.5to 5 hours. The heat treatment time is, particularly for example, 0.1,0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 hours, and can be in therange between the two values exemplified herein.

Heat treatment can be carried out under an inert gas atmosphere such asnitrogen, or under an inert gas atmosphere containing 1 to 4% ofhydrogen.

By performing the heat treatment step at such temperature, thefollowings can be achieved. (1) an effect to increase the ratio ofrutile phase in the carrier powder; (2) an effect to achieve strongfusion of the metal fine particles 130 with the carrier fine particles150; (3) an effect of improving conductivity of carrier metal catalystby enlarging the Ti³⁺ region formed in the vicinity of the metal fineparticles 130

Here, (3) will be explained in further detail.

When the heat treatment is carried out at a temperature of 800° C. orhigher, the Ti atom of the carrier powder would diffuse into the metalfine particles 130. Accordingly, the entirety of the metal fineparticles 130 would become an alloy containing Ti and Pt (the content ofTi would be larger near the center and becomes smaller towards the outerside). Such condition is maintained up to approximately 900° C.,however, when the temperature reaches 920° C. or higher, Pt wouldprecipitate on the surface of the metal fine particles 130 to form askin layer. When the skin layer of Pt is formed, oxygen easily come outof TiO₂ at its vicinity (refer to non-patent literature 1). As a result,the Ti³⁺ region around the metal fine particles 130 would be enlarged,thereby increasing the conductivity of the carrier metal catalyst. Whenthe heat treatment is carried out at 900° C. as in Patent Literature 1,the entirety of the metal fine particles 130 would become an alloyincluding Ti and Pt, and a skin layer of Pt would not be formed.Therefore, the Ti³⁺ region hardly enlarges, and the conductivity couldnot be improved.

After the carrier powder is manufactured by the method disclosed in “3.Method for Manufacturing Carrier Powder” (hereinafter referred to as“flame method”), the carrier powder is preferably not subjected to heattreatment and the supporting step is carried out. The carrier powdermanufactured by the flame method is mostly the rutile phase, however,there is a small portion of the anatase phase. When the supporting stepis carried out with the carrier powder in this condition, the Ti³⁺region tends to become large. On the other hand, when the heat treatmentis carried out after manufacturing the carrier powder by the flamemethod, the anatase phase would change into the rutile phase, and thusthe expansion of the Ti³⁺ region during the supporting step issuppressed. The heat treatment mentioned here is a heat treatment whichchanges the anatase phase into the rutile phase. The heat treatmenttemperature is, for example, 800 to 1000° C., particularly for example,800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930,940, 950, 960, 970, 980, 990, and 1000° C., and can be in the rangebetween the two values exemplified herein.

<Reduction Step>

In the reduction step, reduction treatment of the metal fine particles130 is carried out after the heat treatment step. The reductiontreatment can be carried out by performing a heat treatment under areductive atmosphere containing a reductive gas such as hydrogen.

The temperature of this heat treatment is, for example, 70 to 300° C.,preferably 100 to 200° C. This temperature is, particularly for example,70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250,or 300° C., and can be in the range between the two values exemplifiedherein.

The heat treatment time is, for example, 0.01 to 20 hours, preferably0.1 to 5 hours. The heat treatment time is, particularly for example,0.01, 0.05, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, or 20 hours,and can be in the range between the two values exemplified herein.

When the reductive gas is hydrogen, the density thereof is, for example,0.1 to 100 volume %, preferably 0.2 to 10 volume %, and more preferably0.5 to 3 volume %. This density is, particularly for example, 0.1, 0.2,0.5, 1, 1.5, 2, 2.5, 3, 10, or 100 volume %, and can be in the rangebetween the two values exemplified herein.

The metal fine particles 130 after the heat treatment in the supportingstep can be in an oxidized condition. In such case, the metal fineparticles 130 may not show catalyst activity. The catalyst activity canbe increased by reducing the metal fine particles 130.

EXAMPLES

The carrier metal catalyst was manufactured in accordance with themethod described below, and various evaluations were performed.

1. Manufacture of Carrier Metal Catalyst 100

Example 1

(Manufacture of Carrier Powder)

By using the manufacturing apparatus 1 shown in FIG. 8 to FIG. 11,carrier powder was manufactured. As the burner gas 2 a, gas prepared byblending 5 L/min of oxygen and 1 L/min of propane gas was used. This gaswas ignited to form a flame (chemical flame) 7 of 1600° C. or higher atthe tip of the burner 2. The raw material solution 23 a was prepared byblending titanium octylate and tantalum octylate by a molar ratio of0.95:0.05, and then the blend was further combined with mineral spiritterpen and dissolved. Oxygen was used as the mist gas 13 a. 9 L/min ofthe mist gas 13 a and 3 g/min of the raw material solution 23 a wereblended and sprayed from the tip of the raw material supplying unit 3which is a spray nozzle (atomizer) towards the center portion of theflame, thereby allowing combustion of the blend and generation of thecarrier powder which is an aggregate of the carrier fine particles 150.During such, negative pressure was applied to the gas dischargingportion 5 b to suction air from slit 6 b at a flow rate of 170 L/min,thereby collecting the generated carrier powder in the collector 5 (withfilter 5 a). The raw material supplying unit 3 comprises a double tubestructure (overall length of 322.3 mm). Oxygen is supplied from theouter cylinder 13, and the raw material solution 23 a is supplied to theraw material distribution cylinder 23. At the tip of the raw materialdistribution cylinder 23, a fluid nozzle and an air nozzle are provided,and the raw material solution 23 a was converted into the mist 23 b atthis position. The amount of the carrier powder collected was 10 g ormore when the operation was carried out for 60 minutes.

(Support and Reduction of Metal Fine Particles 130)

In accordance with the procedures in FIG. 12, metal fine particles 130were supported onto the carrier powder.

First, 0.57 mL of chloroplatinic acid hexahydrate aqueous solution wasdissolved in 38 ml of super pure water, followed by addition of 1.76 gof sodium carbonate, and then the mixture was agitated (Step S1 in FIG.12).

The solution was diluted with 150 ml of water, and pH of the solutionwas adjusted to 5 with NaOH. Thereafter, 25 ml of hydrogen peroxide wasadded, and the pH was again adjusted to 5 with NaOH (Step S2 in FIG.12).

To the dispersion, a dispersion prepared by dispersing 0.50 g of carrierpowder in 15 mL of super pure water was added (Step S3 in FIG. 12), andthe mixture was agitated for 3 hours at 90° C. (Step S4 in FIG. 12). Themixture was cooled to room temperature, and was then filtered. Theresidue was washed with super pure water and alcohol, and was then driedovernight at 80° C. The residue was further subjected to 2 hours of heattreatment in nitrogen at 950° C., thereby allowing the metal fineparticles 130 to be supported on the carrier powder. Then, heattreatment was performed for 2 hours in 1% hydrogen at 150° C. to reducethe metal fine particles 130 (Step S5 in FIG. 12). With theseprocedures, carrier metal catalyst 100 having metal fine particles 130supported on carrier powder was obtained.

Example 2

Carrier metal catalyst 100 was manufactured with a similar procedure asExample 1 except that CoCl₂ solution (CoCl₂ (available from KANTOCHEMICAL CO., INC.)/15 mL of super pure water) was added in a dropwisemanner at 2 mL/min, and the solution was agitated in Step S2 in FIG. 12.

Comparative Example 1

Carrier metal catalyst 100 was manufactured with a similar procedure asExample 1 and Example 2 except that the heat treatment temperature inStep S5 was altered from 950° C. to 900° C.

2. Evaluation

<BET Specific Surface Area>

Specific surface area of the carrier powder of Example 1 was measured byBET, which turned out to be 60 m²/g.

<XRD Pattern>

Diffraction pattern obtained by XRD measurement of carrier metalcatalyst 100 of Examples 1 to 2 are shown in FIG. 13A. An enlarged viewof the vicinity of 35 to 55° is shown in FIG. 13B.

In the carrier metal catalyst 100 of Examples 1 and 2, only the peakderived from the rutile phase (2θ=27.24 degrees) was observed, and thepeak derived from the anatase phase (2θ=25.16 degrees) was not observed.Further, when XRD pattern was measured for the carrier powder ofExamples 1 and 2, peak derived from the anatase phase was observed,however, the intension was very weak. The ratio of anatase phase/rutilephase was 0.2 or lower.

In addition, according to FIG. 13B, peak derived from Pt can be observednear 40° and 45°, in the diffraction pattern of Pt/Ta—TiO₂ (Example 1)and PtCo/Ta—TiO₂ (Example 2). These peaks are slightly shifted to thehigher degree side from the peaks derived from pure Pt. Accordingly, itcan be understood that when PtCo and Pt of the metal fine particles 130are subjected to heat treatment, Ti, which is a constituting element ofthe carrier powder, becomes dispersed and dissolved in each of the metalfine particles 130, thereby forming alloys of PtCoTi and PtTi.

<Analysis by TEM Image>

TEM image of the carrier metal catalyst 100 of Examples 1 and 2 areshown in FIG. 6A and FIG. 6B, respectively. Diameter of thecircumscribed circle of all the metal fine particles 130 in the TEMimage of the carrier metal catalyst 100 shown in FIG. 6A and FIG. 6Bwere measured, and then the mean particle size of the metal fineparticles 130 was calculated as their arithmetic mean. In Example 1, themean particle size of the metal fine particles 130 was 6.9 nm, and thestandard deviation was 2.7 nm. In Example 2, the mean particle size ofthe metal fine particles 130 was 7.8 nm, and the standard deviation was3.0 nm.

<Preparation of Fuel Cell>

(Preparation of Anode Catalyst Ink)

First, 0.45 g of carrier metal catalyst 100 and Nafion were blended sothat the volume ratio would be 0.7. Then this mixture, 1.98 g of2-propanol, 2 g of water, and 20 balls of zirconium (5 mm diameter) wereloaded into a pot made of zirconium (available from Fritsch Japan Co.,Ltd, 45 cm³ volume). The content was mixed for 30 minutes by a planetaryball mill (available from Fritsch Japan Co., Ltd, P-6, rotation numberof 270 rpm). The mixture obtained by mixing with the planetary ball millwas further mixed for 2 hours by a mill pot rotating machine (availablefrom NITTO KAGAKU CO., LTD., ANZ-61S, rotation number of 60 rpm). Themixture obtained was allowed to stand still for 24 hours in a cool box(12° C.). The mixture after left to stand still for 24 hours was furthermixed for 1 hour by the mill pot rotating machine, and was subjected tore-dispersion treatment by an ultrasonic homogenizer (available from SMTCO., LTD., UH-50). The mixture obtained from the series of operationshall hereinafter referred to as “anode catalyst ink”.

(Preparation of Cathode Catalyst Ink)

Further, mixture of Pt supported on carbon (Pt/GCB, TEC10EA50E, amountof Pt supported being 46 wt %, available from Tanaka Kikinzoku Kogyo),Nafion, ethanol, and water was prepared in a similar manner as thecathode catalyst ink. In particular, 0.45 g of Pt/GCB and Nafion wereblended so that the volume of Nafion would be 0.7 with respect to thevolume of Pt/GCB. Then this mixture, 3.96 g of ethanol as a volatileorganic compound, 2 g of water, and 20 balls of zirconium (5 mmdiameter) were loaded into a pot made of zirconium (available fromFritsch Japan Co., Ltd, 45 cm³ volume). The content was mixed for 30minutes by a planetary ball mill (available from Fritsch Japan Co., Ltd,P-6, rotation number of 270 rpm). The mixture obtained by mixing withthe planetary ball mill was further mixed for 2 hours by a mill potrotating machine (available from NITTO KAGAKU CO., LTD., ANZ-61S,rotation number of 60 rpm). The mixture obtained was allowed to standstill for 24 hours in a cool box (12° C.). The mixture after being leftto stand still for 24 hours was further mixed for 12 hours by the millpot rotating machine, and was subjected to re-dispersion treatment by anultrasonic homogenizer (available from SMT CO., LTD., UH-50). Themixture of Pt/CB and Nafion thus obtained from the series of operationshall hereinafter referred to as “cathode catalyst ink”.

Pulse swirl spray method (PSS) was used for preparing the anode catalystcoating film (CCM, area: 4.4 cm²). Atomization pressure was adjusted to0.15 MPa, operation pressure was adjusted to 0.4 MPa, and the syringepressure was adjusted to 0.1 MPa, and the temperature of the substratewas adjusted to 55° C. The anode catalyst ink was coated on the polymerelectrolyte membrane (Nafion membrane) several times so that the amountof Pt supported would be approximately 0.5 mg-Pt/cm². Subsequently, thecoating was dried in a thermostatic chamber at 60° C., thereby obtainingan anode CCM (a polymer electrolyte membrane having an anode catalystlayer formed on one side), amount of Pt supported being approximately0.048 to 0.054 mg-Pt/cm².

On the other hand, PSS method was used also for the preparation of theCCM of Pt/GCB. The cathode catalyst ink was coated on the gas diffusionlayer using a carbon paper (GDL, 25BCH, SGL, carbon group). Atomizationpressure was adjusted to 0.15 MPa, operation pressure was adjusted to0.4 MPa, and the syringe pressure was adjusted to 0.1 MPa, and thetemperature of the substrate was adjusted to 55° C. The cathode catalystink was coated on the GDL several times so that the amount of Ptsupported would be approximately 0.5 mg-Pt/cm². Subsequently, thecoating was dried in a thermostatic chamber at 60° C. As a result, acathode gas diffusion electrode (a gas diffusion layer having a cathodecatalyst layer formed thereon) (GDE, catalyst layer area: 4.4 cm²) wasobtained.

In the CCM, the GDE was layered onto the surface of the polymerelectrolyte membrane not having the anode catalyst layer coated thereon,so that the cathode catalyst layer comes into contact with the polymerelectrolyte membrane. The gas diffusion layer (GDL) was furtherlaminated onto the anode catalyst layer of the CCM, and hot pressing wasperformed (140° C., pressure of 10 kgf/cm²) for 3 minutes. Accordingly,a membrane electrode assembly (MEA) prepared by laminating the cathodecatalyst layer and the anode catalyst layer on the polymer electrolytemembrane so that the catalyst layers face each other, was obtained.

Each of the MEA obtained were used to structure a single cell, and wasinstalled in a power generation evaluation device (FCE-1, available fromPanasonic Production Technology).

<Measurement of I-V Characteristics and Cell Resistance>

Relation between current and voltage (I-V) was measured using anelectronic load device (PLZ-664WA, available from Kikusui ElectronicsCorporation). Hydrogen was used as the anode (100 ml/min, atmosphericpressure), and hydrogen or air was used as the cathode with a flow rateof 100 ml/min and a pressure of atmospheric pressured. The temperaturewas kept at 80° C. Cell resistance was measured using a milli-ohm meter(Model 356E, available from Tsuruga Electric Corporation). The cellresistance obtained when the current density flowing through the load is0.5 A/cm² is referred to as “cell resistance measured under standardconditions”.

The result of measuring the I-V characteristics is shown in FIG. 14. Theresult obtained in the measurement of Pt/Ta—TiO₂ catalyst (Example 1),PtCo/Ta—TiO₂ catalyst (Example 2), and commercially available Pt/GCBcatalyst for comparison are shown together. It can be understood thatthe I-V measurement results of Pt/Ta—TiO₂ catalyst and PtCo/Ta—TiO₂catalyst compare favourably with the I-V measurement result ofcommercially available Pt/GCB catalyst. In addition, it can beunderstood that overvoltage is slightly suppressed in the I-Vmeasurement result of PtCo/Ta—TiO₂ catalyst than in Pt/Ta—TiO₂ catalyst.

“Cell resistance measured under standard conditions” of the fuel cellprepared using the carrier metal catalyst 100 of Example 1 and Example 2were measured. The results of measurement are shown in FIG. 14. The cellresistances were 0.069 Ω·cm² in both fuel cells, and is approximatelythe same as the cell resistance of the fuel cell prepared usingcommercially available Pt/GCB. This can be understood from the fact thatthe graphs in the lower region in FIG. 14 are almost overlapped. On theother hand, when the carrier metal catalyst 100 of Comparative Example1, that is, Pt/Ta—TiO₂ catalyst and PtCo/Ta—TiO₂ catalyst subjected toheat treatment at 900° C. were used, the cell resistance of the fuelcells were 0.113 Ω·cm². Accordingly, it became obvious that a cellresistance measured under standard conditions of a fuel cell preparedusing the carrier metal catalyst of 0.090 Ω·cm² or lower can be achievedby performing heat treatment at 950° C. That is, the carrier metalcatalyst of the present invention and the fuel cell prepared by usingthe carrier metal catalyst can exhibit a superior effect so as tosuppress the internal resistance of the fuel cell.

In order to confirm the improvement in performance at the anode side,anode polarization measurement using H₂ pump test was performed. The H₂pump test was performed with the cells used in the cell resistancemeasurement under the conditions shown in Table 1. Here, the hydrogengas supplied to the anode was supplied to the cathode continuously (FIG.15). The anode polarization curve of the cells using PtCo/Ta—TiO₂catalyst, Pt/Ta—TiO₂ catalyst, and commercially available Pt/GCBcatalyst for comparison are shown in FIG. 16. The anode polarizationwhen the PtCo/Ta—TiO₂ catalyst was used was similar to the case wherethe Pt/Ta—TiO₂ catalyst was used, and the value of overvoltage wasslightly higher than the case where Pt/GCB was used. This value was onetenth or less of the case where the carrier metal catalyst 100 wassubjected to heat treatment at 900° C. and as Pt/Ta—TiO₂ catalyst andPtCo/Ta—TiO₂ catalyst. That is, improvement in the performance at theanode side was confirmed in the H₂ pump test for cases where heattreatment was performed at 950° C. Therefore, the present inventionachieves an excellent effect so as to achieve improvement in theperformance of the H₂ pump by applying the present invention in the H₂pump.

FIG. 17 shows a cyclic voltammogram of the PtCo/Ta—TiO₂ catalyst andPt/Ta—TiO₂ catalyst. The electrochemical active area (ECA) obtained fromFIG. 17 was 17.0 m²g⁻¹ for PtCo/Ta—TiO₂, and 17.2 m²g⁻¹ for Pt/Ta—TiO₂.The fact that Pt and PtCo both have similar ECA is an evidence that theoutermost surfaces are covered with the same Pt skin layer. In addition,it can be understood that the waveform peak area from 0.6V to 1.0Vassociated with oxidation reduction of Pt is largely decreased comparedwith the area of the hydrogen adsorption/desorption wave. This indicatesthat the oxygen reduction reaction at the anode has greatly decreased.For example, this indicates that the oxygen reduction reaction at theanode is suppressed at starting/terminating of the fuel cell vehicle. Asa result, the hydrogen generation reaction at the cathode and thereverse current of the proton are suppressed, thereby suppressing carbondegradation at the cathode. That is, the carrier metal catalyst of thepresent invention and the fuel cell using the carrier metal catalystshow an excellent effect so as to suppress cathode catalyst degradationcaused by oxygen reduction reaction at the anode.

TABLE 1 Condition of anode polarization measurement Anode Cathode Gas H₂Flow rate 1 L min⁻¹ Retention 5 min time of step

EXPLANATION OF SYMBOLS

-   1: manufacturing apparatus-   2: burner-   2 a: burner gas-   3: raw material supplying unit-   4: reaction cylinder-   5: collector-   5 a: filter-   5 b: gas discharging portion-   6: gas reservoir-   6 a:cold gas introducing portion-   6 b:slit-   6 c:inner peripheral wall-   6 d:burner insertion hole-   6 g:cold gas-   7: flame-   13: outer cylinder-   13 a: mist gas-   23: raw material distribution cylinder-   23 a: raw material solution-   23 b: mist-   100: carrier metal catalyst-   110: gap-   120: crystallite-   130: metal fine particles-   150: carrier fine particles-   160: branch-   200: solid polymer fuel cell-   201: anode-   202: cathode-   203: load-   210A: gas diffusion layer on the anode side-   210K: gas diffusion layer on the cathode side-   220A: catalyst layer-   220A: catalyst layer on the anode side-   220K: catalyst layer on the cathode side-   230: electrolyte membrane

The invention claimed is:
 1. A carrier metal catalyst, comprising: acarrier powder; and metal fine particles supported on the carrierpowder; wherein the carrier powder is an aggregates of carrier fineparticles; the carrier fine particles comprise a chained portionstructured by a plurality of crystallites being fusion bonded to form achain; the carrier fine particles include titanium oxide; the carrierfine particles are doped with an element having a valence different froma valence of titanium; the titanium oxide of the carrier powder has ananatase phase/rutile phase ratio of 0.2 or lower; the metal fineparticles have a mean particle size of 3 to 10 nm; the metal fineparticles include platinum; and a cell resistance measured understandard conditions of a fuel cell prepared using the carrier metalcatalyst is 0.090 Ω·cm² or lower.
 2. A fuel cell, comprising: a catalystlayer on an anode side, an electrolyte membrane, and a catalyst layer ona cathode side in this order; wherein at least one of the catalyst layeron the anode side or the catalyst layer on the cathode side is formed bythe carrier metal catalyst of claim
 1. 3. The fuel cell of claim 2,wherein the catalyst layer on the anode side is formed by a carriermetal catalyst, comprising: a carrier powder; and metal fine particlessupported on the carrier powder; wherein the carrier powder is anaggregates of carrier fine particles; the carrier fine particlescomprise a chained portion structured by a plurality of crystallitesbeing fusion bonded to form a chain; the carrier fine particles includetitanium oxide; the carrier fine particles are doped with an elementhaving a valence different from a valence of titanium; the titaniumoxide of the carrier powder has an anatase phase/rutile phase ratio of0.2 or lower; the metal fine particles have a mean particle size of 3 to10 nm; the metal fine particles include platinum; and a cell resistancemeasured under standard conditions of a fuel cell prepared using thecarrier metal catalyst is 0.090 Ω·cm² or lower.
 4. A method formanufacturing the carrier metal catalyst of claim 1, comprising: asupporting step; wherein the supporting step comprises an adsorptionstep and a heat treatment step; the adsorption step includes allowingmetal colloidal particles be adsorped on the carrier powder; a metal ofthe metal colloidal particles includes platinum; and the heat treatmentstep includes performing a heat treatment at 920 to 1100° C. after theadsorption step to convert the metal colloidal particle into the metalfine particles.
 5. The method of claim 4, wherein the carrier powder isgenerated via a carrier powder generation step; the carrier powdergeneration step includes thermal decomposition reaction of titaniumcompound at a high-temperature region of 1000° C. or higher, therebygenerating the carrier powder which is the aggregate of carrier fineparticles; the carrier powder generation step is carried out whilesupplying a cold gas to a surroundings of the high-temperature regionthrough a slit provided to a cylinder-shaped gas reservoir; the gasreservoir is provided with a cold gas introducing portion whichintroduces the cold gas into the gas reservoir; and the cold gasintroducing portion is structured so as to allow the cod gas introducedthrough the cold gas introducing portion into the gas reservoir revolvesalong an inner peripheral wall of the gas reservoir.